"If no progress is made at that meeting, Cosatu will mobilise its members for a massive strike as soon as [the National Economic Development and Labour Council] declares that the matter has been duly considered," he said at a media briefing after a meeting of Cosatu leadership.
The Nedlac meeting would take place on June 14, days after the start of the 2010 FIFA World Cup.
Vavi said Cosatu delivered a Section 77 notice to Nedlac in April.
The respondents to this are the department of trade and industry, the department of energy, the department of economic development, Eskom, the National Energy Regulator of SA and others.
At a meeting on May 25, respondents said they did not have a mandate, but agreed to respond in writing to issues raised in the notice before the June 14 meeting.
He said it was Cosatu's right to embark on industrial action.
"When we do so [go on strike] no one must accuse us of holding anyone to ransom," Vavi said.
Cosatu was being supported by the Federation of Unions of SA in its attempt to reverse the high price of electricity in the country.
Cosatu had also met the ANC to discuss the energy matter.
Vavi said these talks were being taken forward and if a solution was found in this process there would no longer be a need to engage in the legal processes through Nedlac.- Sapa